Stewart Warner Temperature Sender

Mate, I dare say that the original sender will work. I think the instructions quote a range of resistance which is compat*table with your gauge. For arguments sake I have just installed a new fuel tank sender and the old gauge works fine (it's over 20 years old) although I did pull the needle off and tweak it slightly before sealing it all up again, so I didn't need the new gauge which looked out of place. If you're keen you can immerse the sender in a pot on the stove and note the temp when it boils (100 celcius equals 212 farenheit, and you'll need to hook up the gauge to all its wires - sender to gauge, +ve and -ve to a 12 volt source and presumably also ground the body of the sender to the -ve. Go to Dick Smith and get a packet of little jumper leads, they're all different colours and about a foot long. Perfect for this kind of job). That should give you some confidence. The temperature, oil pressure and fuel gauges all work on the same principle.